. (a) Why does common salt get wet during the rainy season

(a) Why does common salt get wet during the rainy season?

(b) How can this impurity be removed?

(c) Name a substance which changes the blue colour of copper sulphate crystals to white.

(d) Name two crystalline substances which do not contain water of crystallisation.



Best Answer

a. Table salt turns moist and ultimately forms a solution on exposure to air especially during the rainy season. Although pure sodium chloride is not deliquescent, the commercial version of the salt contains impurities (such as magnesium chloride) which are deliquescent substances.

b. The impurity can be removed by passing a current of dry hydrogen chloride gas through a saturated solution of the affected salt. Pure sodium chloride is produced as a precipitate which can be recovered by filtering and washing first with a little water and finally with alcohol.

c. Conc. sulphuric acid

d. Common salt and sugar


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